Current portable terminal device such as a cellular phone has its structure and operating method more and more diversified due to diversification of service and multi-function of terminals. Proposed are, for example, a portable terminal having a structure to execute screen operation or character input only through a touch panel or a touch sensor provided on a display screen without the provision of a hard key and a portable terminal device having a structure to enable switching of a state of no operation key which enables simple operation by a touch panel or a touch sensor, a vertically long screen state suitable for telephone communication and mail operation and a horizontally long screen state suitable for one-segment broadcasting viewing and full-browser operation according to a purpose of use.
Examples of portable terminal devices of this kind are disclosed in, for example, Patent Literature 1 and Patent Literature 2.
The portable information terminal recited in the Patent Literature 1 has a structure comprising a first connecting shaft which connects an operation unit casing and a display unit casing so as to open and close and a second connecting shaft which allows the display unit casing in an open state to rotate laterally, which structure enables the display unit casing to open to have the vertically long screen state and further enables the display unit casing in the open state to be laterally positioned to switch to the horizontally long screen state.
Also disclosed in Patent Literature 1 is a structure in which with a third rotation shaft that allows the display unit casing in the open state to rotate inside out, the display unit casing is superposed on the operation unit casing with its display surface as the upper side to have the no-operation key state by closing the display unit casing inside out.
Furthermore, the portable terminal recited in Patent Literature 2 has a structure in which the display unit casing is superposed on the operation unit casing to have the no-operation key state, the display unit casing is slid upwardly on the operation unit casing to have a vertically long screen and the display unit casing in the vertically long screen state is further rotated to have a horizontally long screen.    Patent Literature 1: WO 2006-038554A    Patent Literature 2: Japanese Patent Laying-Open No. 2008-92264.
A portable terminal structured to execute screen operation and character input only by a touch panel or a touch sensor provided on a display screen with no hard key provided has a shortcoming that while such operation as selection of an input item on the screen or screen scrolling can be realized with relative ease by using a touch panel, operability of character input is considerably reduced as compared with hardware key switching.
The portable terminal recited in Patent Literature 1 structured to open a display unit casing to have the vertically long screen state, laterally position the display casing being opened to switch to the horizontally long screen state and further close the display unit casing inside out to have the no-operation key state has a shortcoming that switching from the vertically long screen state to the horizontally long screen state and further switching to the no-operation key state cannot be realized with ease only by one hand holding the terminal.
Furthermore, while the portable terminal recited in Patent Literature 1 enables one hand holding the terminal to realize key operation using the key input unit in the vertically long screen state or the horizontally long screen state, with respect to operation by the touch panel on the screen, it requires a hand holding the terminal to be switched in order to make a thumb of the hand holding the terminal reach the whole area of the touch panel or requires operation by using the other free hand. It therefore has a problem that both of the operations using the key input unit and the touch panel cannot be executed comfortably only by one hand holding the terminal.
When both a touch panel and a hard key are mounted on a cellular phone or the like, it has been difficult to operate both the touch panel and the hard key while holding the operation unit by one hand without switching the hand holding the device because of a structure of the casing. When a touch panel is added as an input device to a portable terminal comprising a key operation unit as a hard key, a casing should be designed to allow comfortable operation of both the key operation unit and the touch panel.
The portable terminal recited in Patent Literature 2 has a problem that because the display unit fails to have a touch panel, character inputting and screen operation should be executed only by key operation using a key input unit of the operation unit casing, resulting in having considerably inferior operability in screen operation as compared with a portable terminal having a touch panel.
In addition, to be brought into the horizontally long screen state, the portable terminal recited in Patent Literature 2 needs to be once put into the vertically long screen state from the no-operation key state by the sliding of the display unit casing along the operation unit casing upwardly and also to be brought into the no-operation state from the horizontally long screen state, needs to be once put into the vertically long screen state from the horizontally long screen state. It is therefore impossible to directly switch from the no-operation key state to the horizontally long screen state and from the horizontally long screen state to the no-operation key state. In other words, switching from the no-operation key state to the horizontally long screen state and from the horizontally long screen state to the no-operation key state is impossible unless passing through the vertically long screen state, so that state switching operation costs labor.